The present disclosure is directed to high pressure fluid rotary nozzle systems. In particular, embodiments of the present disclosure are directed to an apparatus for retarding the speed of rotation of such rotary nozzles.
High pressure water jet cleaning devices utilizing reaction force rotary nozzles tend to rotate at very high speeds. In many applications it is desirable to slow down such rotary nozzle speed to maximize usable lifetime of the rotary nozzle and effectively improve the cleaning efficiency of such nozzles. A speed reducing device fastened to the shaft of such rotary nozzles is often utilized to retard rotation of the nozzle. Typical viscous fluid speed reducing devices utilize a viscous fluid flowing along a tortuous flow path in a confined space around the rotating shaft to generate a drag on the nozzle shaft.
Typically the operational lifetime of the speed reducing device is limited by the longevity of the bearings and the medium such as a viscous fluid utilized to produce the speed retardation. As an example, the useful lifetime without maintenance of conventional viscous speed retarders is on the order of 40-60 device operating hours. A typical retarder device has a bearing supported shaft connected to the rotary nozzle such that the shaft rotates with the nozzle. A generally cylindrical housing contains the two support bearings supporting the rotating shaft and contains the retarding mechanism. One such retarding mechanism has a series of roller bearings immersed in a viscous fluid within the housing and between end support bearings that are also immersed in the viscous fluid. Another exemplary conventional retarder is a Warthog WG-1 by Stoneage Inc. This retarder has end support bearings sandwiching a large diameter drag sleeve fastened to or integrally formed around the shaft in the housing instead of utilizing a series of bearings in the viscous fluid. These support bearings and the drag sleeve are immersed in the viscous fluid contained within the cylindrical housing. Together the support bearings and the retarding drag sleeve are contained between two shaft seals, sealing the shaft to the housing, and preventing escape of the viscous fluid. Thus the end support bearings and the drag sleeve in the WG-1 are immersed in viscous fluid and function together to retard the speed of the rotating nozzle.
As the retarder rotates in the housing, the viscous fluid is circulated (pumped) within the fluid chamber by a helical groove around the outer surface of the drag sleeve portion of the shaft and through a series of axially extending bores through the drag sleeve portion of the shaft. Additionally, the helical groove serves to uniformly distribute the fluid above the drag sleeve and through the end bearings. In the immersed bearing system, drag is created as a function of the fluid viscosity, the bearing geometry, the surface area of the drag sleeve and the gap size between the drag sleeve and the cylindrical housing. This implementation of a viscous fluid retarder creates drag, and also eventually degrades the viscosity of the viscous fluid. Once the viscous fluid degrades during operation, the rotary nozzle speed increases substantially, frequently audibly indicating to an operator that the viscous fluid needs to be changed. The retarder and nozzle then must be removed from service, disassembled, cleaned and flushed, reassembled and new viscous fluid installed. This is inconvenient to the operator, takes maintenance down time and can result in increased maintenance costs over the life of the tool. Therefore what is needed is a viscous retarder device that has a substantially improved operational lifetime in order to solve these problems.